Vinyl? (the same stuff used on cars for signs & full vehicle wraps) Not to sure how it would stick to tubes though. That way you could get the british flag printed (rather than cut- looks better) out onto it and it would look pritty good. If it worked, you could cover it again with clear vinyl as protection.
Printing onto a piece of hypalon would be most durable, but wouldnt know if the ink will stick like it does with other things.